Modellierung und Regelung von dielektrischen Mehrschicht-Elastomerwandlern
Format: 17,0 x 24,0 cm
Publishing year: 2020
Electromechanical transducers based on dielectric elastomers (DE) can be operated as actuators, generators and sensors. Compared to classic electromagnetic actuators the intrinsic material properties offer significant
advantageous e.g. concerning the energy efficiency and density enabling
amongst others miniaturization potentials. Researching intelligent supply and control concepts, for example for a combined actuator-sensor-operation, allow to exploit the full potential of these novel transducers with the corresponding benefits compared to conventional transducer systems. For this purpose, within this thesis novel estimator and control concepts based on a holistic transducer
model including the driving power electronics and the DE transducer are carried out that enable a combined actuator-sensor-operation in closed
In particular, multilayer DE stack-transducers are considered here. They represent a transducer class with high force density as they almost completely consist of active material. Their capacitive behavior requires a particular driving electronics to supply the transducers withhigh electric field strengths resulting in voltages in the lower kilovolt range. Here, a bidirectional flyback converter is used for this
purpose enabling a high energy efficiency due to the bidirectional energy flow.
At first, model based control concepts for the closed loop current and voltage control are designed and validated. The superimposed, application specific control of the DE transducer uses this inner control as interface. In order to reduce the measurement instrumentationand effort, control quantities are estimated with a model so that no current measurement is necessary for the closed loop operation of the converter.
Afterwards, an analytical DE transducer model is derived, parameterized and experimentally validated. The model is based on a power balance to combine the mechanical dynamics of the elastomer material with the electrical dynamics of the overall transducer. On the one hand, the model is used for the design of the final control concepts. On the otherhand, state and disturbance estimators are developed based on this model and an extended Kalman filter. These estimators are required for the operation of the DE transducer in closed loop. Beside a sensor basedestimator, that uses the measured terminal voltage and the transducer deformation, also a self-sensing estimator for the combined actuator-sensor-operation is derived, that estimates the mechanical transducer state using the measured terminal voltage and current. In contrast to existing approaches, here no superimposed excitation is required.
Finally, a position as well as a universal energy control are designed. The latter allows to control the force, deformation or voltage of the DE transducer. Due to the utilized switched mode power supply the sliding mode control approach is carried out, as it is well suited for the particular properties of the control plant. Novel optimizations and adaptations enable highly dynamic sensor based and self-sensing closed loop operation with a maximum bandwidth of up to 300 Hz, as well as highaccuracy during steady state and significantly reduced switching frequencies.